1. Field of the Invention
The present invention relates to a vibration-type driving apparatus, and more particularly to a vibration-type driving apparatus having a structure in which a vibrator is pressed and contacted to a driving member.
2. Related Background Art
A vibration-type driving apparatus (vibration wave motor) is adapted so that vibrators, each having an electro-mechanical energy conversion element (for example, a piezoelectric element) and an elastic member (mainly of metal) connecting the electro-mechanical energy conversion elements, excites vibrations of a plurality of vibration modes.
Vibrations of the plurality of vibration modes are synthesized to generate an ellipsoidal movement of a surface of the elastic member, and relatively drive the driving member contacting the elastic member. Various types of such vibration-type driving apparatuses have been proposed, and particularly, many vibration-type driving apparatuses have been proposed as actuators that rotationally drive a lens barrel of a camera.
Among these apparatuses, many actuators have been recently proposed having a structure with a combination of plate shape vibrators (chip shaped vibrators) having a rectangular vibrating portion as a type that can both save space and reduce cost and has high flexibility in design of size or shape of a lens barrel.
As a vibration-type driving apparatus including a combination of such chip shaped vibrators, U.S. Pat. No. 6,078,438 proposes a vibration-type driving apparatus as described below.
This apparatus includes a chip shaped vibrator having at least one vibration node, a supporting member that supports the vibrator, and a rotatable rotor (driving member), and the supporting member also serves as a pressing spring that urges a pressing force between the rotor and the vibrator.
The supporting member and the pressing spring are adapted so that a part of a ring-shaped base is bent in a rotational axis direction (pressing direction) by bending in a cantilever, and the vibrator is independently supported at an end thereof.
U.S. Pat. No. 7,466,062 proposes a vibration-type driving apparatus having a structure in which a vibrator has a shape (block shape) with a thickness in a pressing direction, and the vibrator is independently supported and pressed as in U.S. Pat. No. 6,078,438.
In the apparatuses in U.S. Pat. No. 6,078,438 and U.S. Pat. No. 7,466,062, a member for supporting the vibrator and a pressing spring are shared. This reduces support rigidity, but such a structure has a problem as described below.
Specifically, when the rotor is in a non-driving state and no driving reaction is applied to the vibrator, a satisfactory contact state between the vibrator and the rotor is maintained.
However, when a driving force is generated in the vibrator, a rotational moment is generated between the contact portion with the rotor and the supporting portion in the vibrator. Thus, if support rigidity (rotation rigidity) of the vibrator is low, the vibrator is easily tilted with respect to a sliding surface of the rotor.
This causes non-uniform contact plane pressure of the vibrator to worsen the contact state with the rotor, which may reduce output or cause abnormal noise such as a squeak.
In view of the above-described problem, the present invention has a driving member to provide a vibration-type driving apparatus that can configure a vibrator holder that maintains low rigidity of a vibrator in a pressing direction and has high rigidity for a rotational moment applied to the vibrator by driving, and can stably maintain a contact state between the vibrator and a driving member.